Electrophysiological correlates of predictive coding of auditory location in the perception of natural audiovisual events

In many natural audiovisual events (e.g., a clap of the two hands), the visual signal precedes the sound and thus allows observers to predict when, where, and which sound will occur. Previous studies have reported that there are distinct neural correlates of temporal (when) versus phonetic/semantic (which) content on audiovisual integration. Here we examined the effect of visual prediction of auditory location (where) in audiovisual biological motion stimuli by varying the spatial congruency between the auditory and visual parts. Visual stimuli were presented centrally, whereas auditory stimuli were presented either centrally or at 90° azimuth. Typical sub-additive amplitude reductions (AV − V < A) were found for the auditory N1 and P2 for spatially congruent and incongruent conditions. The new finding is that this N1 suppression was greater for the spatially congruent stimuli. A very early audiovisual interaction was also found at 40–60 ms (P50) in the spatially congruent condition, while no effect of congruency was found on the suppression of the P2. This indicates that visual prediction of auditory location can be coded very early in auditory processing

Increased sub-clinical levels of autistic traits are associated with reduced multisensory integration of audiovisual speech

Recent studies suggest that sub-clinical levels of autistic symptoms may be related to reduced processing of artificial audiovisual stimuli. It is unclear whether these findings extent to more natural stimuli such as audiovisual speech. The current study examined the relationship between autistic traits measured by the Autism spectrum Quotient and audiovisual speech processing in a large non-clinical population using a battery of experimental tasks assessing audiovisual perceptual binding, visual enhancement of speech embedded in noise and audiovisual temporal processing. Several associations were found between autistic traits and audiovisual speech processing. Increased autistic-like imagination was related to reduced perceptual binding measured by the McGurk illusion. Increased overall autistic symptomatology was associated with reduced visual enhancement of speech intelligibility in noise. Participants reporting increased levels of rigid and restricted behaviour were more likely to bind audiovisual speech stimuli over longer temporal intervals, while an increased tendency to focus on local aspects of sensory inputs was related to a more narrow temporal binding window. These findings demonstrate that increased levels of autistic traits may be related to alterations in audiovisual speech processing, and are consistent with the notion of a spectrum of autistic traits that extends to the general population

Suppression of the auditory N1 by visual anticipatory motion is modulated by temporal and identity predictability

The amplitude of the auditory N1 component of the event-related potential (ERP) is typically suppressed when a sound is accompanied by visual anticipatory information that reliably predicts the timing and identity of the sound. While this visually-induced suppression of the auditory N1 is considered an early electrophysiological marker of fulfilled prediction, it is not yet fully understood whether this internal predictive coding mechanism is primarily driven by the temporal characteristics, or by the identity features of the anticipated sound. The current study examined the impact of temporal and identity predictability on suppression of the auditory N1 by visual anticipatory motion with an ecologically valid audiovisual event (a video of a handclap). Predictability of auditory timing and identity was manipulated in three different conditions in which sounds were either played in isolation, or in conjunction with a video that either reliably predicted the timing of the sound, the identity of the sound, or both the timing and identity. The results showed that N1 suppression was largest when the video reliably predicted both the timing and identity of the sound, and reduced when either the timing or identity of the sound was unpredictable. The current results indicate that predictions of timing and identity are both essential elements for predictive coding in audition

Atypical visual-auditory predictive coding in Autism Spectrum Disorder:Electrophysiological evidence from stimulus omissions

Autism spectrum disorder is a pervasive neurodevelopmental disorder that has been linked to a range of perceptual processing alterations, including hypo- and hyperresponsiveness to sensory stimulation. A recently proposed theory that attempts to account for these symptoms, states that autistic individuals have a decreased ability to anticipate upcoming sensory stimulation due to overly precise internal prediction models. Here, we tested this hypothesis by comparing the electrophysiological markers of prediction errors in auditory prediction by vision between a group of autistic individuals and a group of age-matched individuals with typical development. Between-group differences in prediction error signaling were assessed by comparing event-related potentials evoked by unexpected auditory omissions in a sequence of audiovisual recordings of a handclap in which the visual motion reliably predicted the onset and content of the sound. Unexpected auditory omissions induced an increased early negative omission response in the autism spectrum disorder group, indicating that violations of the prediction model produced larger prediction errors in the autism spectrum disorder group compared to the typical development group. The current results show that autistic individuals have alterations in visual-auditory predictive coding, and support the notion of impaired predictive coding as a core deficit underlying atypical sensory perception in autism spectrum disorder.  Lay abstract:  Many autistic individuals experience difficulties in processing sensory information (e.g. increased sensitivity to sound). Here we show that these difficulties may be related to an inability to process unexpected sensory stimulation. In this study, 29 older adolescents and young adults with autism and 29 age-matched individuals with typical development participated in an electroencephalography study. The electroencephalography study measured the participants’ brain activity during unexpected silences in a sequence of videos of a handclap. The results showed that the brain activity of autistic individuals during these silences was increased compared to individuals with typical development. This increased activity indicates that autistic individuals may have difficulties in processing unexpected incoming sensory information, and might explain why autistic individuals are often overwhelmed by sensory stimulation. Our findings contribute to a better understanding of the neural mechanisms underlying the different sensory perception experienced by autistic individuals

Electrophysiological alterations in early auditory predictive processing as potential markers for autistic symptomatology

Autism spectrum disorder (ASD) is a pervasive neurodevelopmental disorder that has been linked to a range of perceptual processing alterations, including hypo- and hyperresponsiveness to auditory stimulation. A recently proposed theory that attempts to account for these symptoms suggest that autistic individuals have a decreased ability to anticipate upcoming sensory stimulation. In a series of ERP experiments, we show that autistic individuals have alterations in the early processing of both highly predictable self-initiated auditory stimulation (van Laarhoven, Stekelenburg, Eussen, & Vroomen, 2019), and unexpected omissions of auditory stimulation that is predictable by visual motion (van Laarhoven, Stekelenburg, Eussen, & Vroomen, 2020). In addition, deviancy detection of auditory speech is reduced in autistic individuals, while deviancy detection of visual speech and incongruent audiovisual speech seems to be intact (van Laarhoven et al., in prep). Our findings suggest that autistic individuals may indeed experience difficulties in anticipating upcoming auditory stimulation. Importantly, these difficulties might be due to domain-specific alterations, rather than general impairments in predictive coding. This notion provides potential avenues for future research on electrophysiological markers for autistic symptomatology

Electrophysiological alterations in motor‐auditory predictive coding in autism spectrum disorder

The amplitude of the auditory N1 component of the event‐related potential (ERP) is typically attenuated for self‐initiated sounds, compared to sounds with identical acoustic and temporal features that are triggered externally. This effect has been ascribed to internal forward models predicting the sensory consequences of one's own motor actions. The predictive coding account of autistic symptomatology states that individuals with autism spectrum disorder (ASD) have difficulties anticipating upcoming sensory stimulation due to a decreased ability to infer the probabilistic structure of their environment. Without precise internal forward prediction models to rely on, perception in ASD could be less affected by prior expectations and more driven by sensory input. Following this reasoning, one would expect diminished attenuation of the auditory N1 due to self‐initiation in individuals with ASD. Here, we tested this hypothesis by comparing the neural response to self‐ versus externally‐initiated tones between a group of individuals with ASD and a group of age matched neurotypical controls. ERPs evoked by tones initiated via button‐presses were compared with ERPs evoked by the same tones replayed at identical pace. Significant N1 attenuation effects were only found in the TD group. Self‐initiation of the tones did not attenuate the auditory N1 in the ASD group, indicating that they may be unable to anticipate the auditory sensory consequences of their own motor actions. These results show that individuals with ASD have alterations in sensory attenuation of self‐initiated sounds, and support the notion of impaired predictive coding as a core deficit underlying autistic symptomatology

Predictive coding in autism spectrum disorder:Electrophysiological alterations in early auditory predictive processing as potential markers for autistic symptomatology

Background :  Autism spectrum disorder (ASD) is a pervasive neurodevelopmental disorder that has been linked to a range of perceptual processing alterations, including hypo- and hyperresponsiveness to auditory stimulation. A recently proposed theory that attempts to account for these symptoms suggest that autistic individuals have a decreased ability to anticipate upcoming sensory stimulation. Objectives :  If the ability to anticipate upcoming sensory stimulation is indeed decreased in ASD, perception in ASD could be less affected by prior expectations and more driven by sensory input. Here, we tested this hypothesis with a series of event-related potential (ERP) studies in which we examined the neural correlates of motor-auditory prediction (N1 attenuation), visual-auditory prediction error (omission N1) and deviancy detection of auditory, visual and audiovisual speech (MMN). Methods :  In a series of ERP studies, we first compared the electrophysiological brain response to self- versus externally-initiated tones between a group of individuals with ASD and a group of age matched individuals with typical development. Next, we assessed between-group differences in prediction error signaling by comparing ERPs evoked by unexpected auditory omissions in a sequence of audiovisual recordings of a handclap in which the visual motion reliably predicted the onset and content of the sound. Finally, we examined between group differences in deviancy detection of auditory, visual and audiovisual speech by applying a MMN paradigm. Results :  The results of our first ERP study showed that, unlike in age-matched participants with typical development, self-initiation of tones through a button press did not attenuate the auditory N1 in autistic individuals, indicating that the ability to anticipate the auditory sensory consequences of self-initiated motor actions might be decreased in ASD (van Laarhoven, Stekelenburg, Eussen, & Vroomen, 2019, https://doi.org/10.1002/aur.2087). The results of our second study showed that unexpected omissions of a sound of which the timing and content could be predicted by preceding visual anticipatory motion elicited an increased early auditory omission response (oN1) in the ASD group, indicating that violations of the prediction model produced larger prediction errors in autistic individuals when compared to their peers with typical development (van Laarhoven, Stekelenburg, Eussen, & Vroomen, 2020, https://doi.org/10.1177%2F1362361320926061). Finally, the results of our third study showed that deviancy detection of auditory speech is reduced in autistic individuals, while deviancy detection of visual speech and incongruent audiovisual speech seems to be intact (van Laarhoven et al., in prep). Conclusions :  Taken together, our findings suggest that individuals with ASD may indeed experience difficulties in anticipating upcoming auditory stimulation. Importantly, these difficulties might be due to domain-specific alterations, rather than general impairments in predictive coding. This notion provides potential avenues for future research on electrophysiological markers for autistic symptomatology

Naso-temporal asymmetry in the N170 for processing faces in normal viewers but not in developmental prosopagnosia

Abstract Some elementary aspects of faces can be processed before cortical maturation or after lesion of primary visual cortex. Recent findings suggesting a role of an evolutionary ancient visual system in face processing have exploited the relative advantage of the temporal hemifield (nasal hemiretina). Here, we investigated whether under some circumstances face processing also shows a temporal hemifield advantage. We measured the face sensitive N170 to laterally presented faces viewed passively under monocular conditions and compared face recognition in the temporal and nasal hemiretina. A N170 response for upright faces was observed which was larger for projections to the nasal hemiretina/temporal hemifields. This pattern was not observed in a developmental prosopagnosic. These results point to the importance of the early stages of face processing for normal face recognition abilities and suggest a potentially important factor in the origins of developmental prosopagnosia. © 2004 Elsevier Ireland Ltd. All rights reserved. Keywords: N170; Prosopagnosia; Naso-temporal asymmetry; Non-LGN based vision; Subcortical visual processing Research on human visual abilities through normal lifespan and in brain damage draws attention to visual abilities of the brain that are not based on pathways critically involving latero-geniculate nucleus (LGN). Findings of several studies Evidence for visual abilities not based on LGN-cortical pathways has also been obtained in a very different population, patients with hemineglect [21] and patients with complete unilateral lesion of striate cortex who show residual visio

Characteristics and Outcomes of Patients with Eclampsia and Severe Pre-eclampsia in a Rural Hospital in Western Tanzania: A Retrospective Medical Record Study.

Eclampsia and pre-eclampsia are well-recognized causes of maternal and neonatal mortality in low income countries, but are never studied in a district hospital. In order to get reliable data to facilitate the hospital's obstetric audit a retrospective medical record study was performed in Ndala Hospital, Tanzania. All patients diagnosed with severe pre-eclampsia or eclampsia between July 2011 and December 2012 were included. Medical records were searched immediately following discharge or death. General patient characteristics, medical history, obstetrical history, possible risk factors, information about the current pregnancy, antenatal clinic attendance and prescribed therapy before admission were recorded. Symptoms and complications were noted. Statistical analysis was done with Epi Info®. Of the 3398 women who gave birth in the hospital 26 cases of severe pre-eclampsia and 55 cases of eclampsia were diagnosed (0.8 and 1.6%). Six women with eclampsia died (case fatality rate 11%). Convulsions in patients with eclampsia were classified as antepartum (44%), intrapartum (42%) and postpartum (15%). Magnesium was given in 100% of patients with eclampsia and was effective in controlling convulsions. Intravenous antihypertensive treatment was only started in 5% of patients. Induction of labour was done in 29 patients (78% of women who were not yet in labour). Delivery was spontaneous in 67%, assisted vaginal (ventouse) in 14% and by Caesarean section in 19% of women. Perinatal deaths occurred in 30% of women with eclampsia and 27% of women with severe pre-eclampsia and were associated with low birth weight and prolonged time between admission and birth. 2.4% of women were diagnosed with severe pre-eclampsia or eclampsia. The case fatality rate and overall perinatal mortality were comparable to other reports. Better outcomes could be achieved by better treatment of hypertension and starting induction of labour as soon as possible